Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $57.49   9.484%   $62.9424   $62.94   $62.95   $62.90  
  Purchase #2 $133.97   8.593%   $145.482   $145.48   $145.50   $145.50  
  Purchase #3 $228.84   3.232%   $236.2361   $236.24   $236.25   $236.20  
  Purchase #4 $220.60   9.466%   $241.482   $241.48   $241.50   $241.50  
  Purchase #5 $23.85   4.844%   $25.0053   $25.01   $25.00   $25.00  
  Purchase #6 $163.69   13.330%   $185.5099   $185.51   $185.50   $185.50  
  Purchase #7 $86.93   9.861%   $95.5022   $95.50   $95.50   $95.50  
  7 purchase totals = $915.37       $992.1599   $992.16   $992.20   $992.10